Descenders

Alright so this one isnt that bad i managed to do it in a couple of tries
1.In order to get to the volcano you have to get each of the fire nodes on each of the maps it will be a fire symbol just keep doing the tracks till you find it then jump through the ring of fire on each of the boss jumps.
2.For the boss jumps make sure you have enough speed and akways keep your bike steady
but not too fast as you will not be able to land the jump practice them before attempting Volcano.
3.Always try and do the bonus objectives to get the extra lives do them for highlands and forests as the later ones are alot harder.
4.Once you have a decent amount of lives 10 or more avoid all the objectives and stunts
go off road and just take your time no rush.
5.Most important thing to do is always use LT to break it is amazing it saved me so many times
6. Once you do the peaks boss jump you will be taken to Volcano its very easy to fault here so use break alot once you get to the jump just go as fast as you can and you should make it

I hope this helps
Good luck!!

Getting to Volcano
Volcano is a secret stage in Career mode
To reach Volcano region, you will need to successfully land the Fireball variant boss jump on all four stages in one career session.

To get a shot at the Fireball boss jump, look around the map for the Fire Node.


completing this level will make the boss level icon have a fire shaped outline.


When you reach the boss jump, there will be a helicopter dangling a ring of fire somewhere over the jump. You need to Make the boss jump, going through the ring of fire and landing successfully



Starting at Highlands, you need to complete each region's Fire Node and Fireball boss jump in one run. You will know that you have done this if the text showing your stunts, you see (coloured purple) the name of the boss jump and the a separate stunt called Fireball, or the name of the boss jump stunt with Fireball at the end.
You then need to land the stunt without bailing and go on to complete the level (you cannot restart or go back to a checkpoint after completing it or you will have to try again).

When you reach the peaks boss jump, if you have done everything correct, the wooden landing zone will have flames along each side.

{Thought I was screwed when the weather was bad on the final level}
And instead of the session ending when you press continue , you will be taken to Volcano.

For me, the achievement popped as soon as I loaded into the first Volcano Level. If not, finish the stage as normal. There are no stunts, just bumpy terrain (like Desert). The Volcano Boss jump is to jump the cinder cone of an active volcano. Just hit the front as close to center as you can with a lot of speed, keep it straight and bunny-hop and it should not be much of a problem (I made it third try IRC).

Tips for getting to Volcano
Fire Nodes are tricky, and it can take a lot of trial an error to get the fireball boss jumps right. You are going to want to strike a balance of gaining rep/completing bonus objectives in order to have enough lives and unlock helpful Crew Members. But also, you want to avoid risks to make sure you do not run out of lives.
- Take it steady on difficult levels
- Look for easy levels to farm lives and rep wherever you feel comfortable (You could farm up in Highlands as it is easy, then hope you can land the boss jump at night)
- Make your way across the level select map to the boss jump in as short a route as you can to avoid having to do boss jumps at dusk/night. Also the Fire Node in my experience is often near the boss track.
- If you can't find the boss track, look to pick nodes that unlock the most other nodes possible.
- Look to take advantage of easy stunts for more rep and avoid or go around stunts that you struggle with. Feel free to go off track if it is easiest.
- for boss jumps, look to your speedometer to judge the best speed for each jump, too fast or too slow and you might still make the jump, but miss the ring of fire. adjust your speed as you need to with braking, or turning around at the checkpoint for more of a run up.
- Always aim to hit the ramp dead center and straight. Speed wobbles reduction crew member helps massively
- If you land the jump but missed the ring of fire, do not go through the end level gate, slow down, and press respawn - this will take you to your last checkpoint without losing any health.

Best Crew Members
Top Tier
Green You can bail harder before losing multiple health at once. - More lives to work with
Green Increases chances of staying on your bike when landing hard. - Easier to land boss jumps and safer all round
Green Decreases speed wobbles when going fast. - Lining up boss jumps is far easier
Blue Be able to scout further nodes on the world map. - See where Fire Node is on the map a lot easier

Good to have Tier
Yellow Makes the path wider and the berms higher. - safer, though I don't think it makes boss jump ramps wider
Green Increases the amount of in-air prediction to correct your bike automatically. - Can be a help, and seemed like boss jumps were easier
Yellow Places more checkpoints on the track. - Easier progress if you bail
Yellow Smoothens out the path curves in tracks. - Boss jumps and tracks in general are easier when straight
Yellow Lowers the curvature of all tracks. - Boss jumps and tracks in general are easier when straight
Blue Prevents storm and no-path tracks. - Both can be a hindrance
Yellow Encounter fewer obstacles & trees off the track. - Safer, good for off road short cuts

All other crew members, down to preference, but I'd go for the above if available. Balance whilst riding backwards crew member might just save you a life if you mess up, others probably only a help when it comes to gaining rep.

I will update with screenshots and a video once TA.com picks up the captures